1. Field
The disclosed embodiment relates to the field of structures that incorporate composite material parts that are assembled together.
More particularly, the disclosed embodiment relates to a process for assembling parts made from thermoplastic composite materials.
2. Brief Description of Related Developments
In the field of structures, it is known to produce thermoplastic composite material parts, that is to say parts in which the mineral or organic fibers are held in a reversible rigid matrix that becomes plastic starting from a certain temperature above their anticipated service temperatures.
The thermoplastic properties are in particular exploited during the manufacture of the parts and in particular the forming thereof.
The thermoplastic material parts, once made, are ally assembled in conventional manners by added-en fastening elements, for example rivets, or by adhesive bonding.
It is also known to produce assemblies of parts made of thermoplastic composite material by thermoplastic welding techniques.
In thermoplastic welding, the temperature of the parts to be assembled is raised above the melting point of the resin, the parts are placed in the position of the assembly and a pressure is exerted for a certain time until the resin cools in order to obtain mechanical bonding of the assembled zone.
It is thus known to place the parts in molds in order to heat the parts and to exert, in their joining zones, pressures between the parts in order to obtain the joining thereof.
These methods require a precise holding of the parts during the welding and involves a high energy consumption or the heating.
For heating the material at a temperature above the melting point of the thermoplastic resin, it is also known to provide heating energy by induction heating.
In this case, Foucault currents are generated at the interface to be welded by means of a head that produces by an alternating magnetic field. A metal element such as a wire mesh, in which the induced currents will be concentrated by the magnetic field and will produce heat by the Joule effect, is placed at the interface.
In order to carry out the assembly operation, the intimate contact of the parts is generally ensured by a local pressure of the head providing the heating energy and the head is displaced along the weld line.
In this thermoplastic welding fastening method, it is necessary for the pressure between the two parts to be produced for a sufficient time and it results from this requirement that the speed of displacement of the head, which exerts the pressure, and therefore the welding speed, is limited, which does not make it possible to obtain all the advantages of induction heating.
The use of electrically conductive wire meshes placed at the interface of the parts that have to be welded additionally has the drawback of creating temperature inhomogeneities, in particular at the ends of the welding lines, that are prejudicial to the quality of the welding and lead to assembled parts being rejected.